Hi Yves.... I did the same thing to my 8 inch Nexstar 8 about a week ago. I contacted Celestron and they told me that it would cost $500 plus shipping for replacement.. Evidently you cannot just buy/install a new collector plate... It must be matched and aligned on their optical bench.
I also contacted Mike Swanson who is about the most knowledgeable person regarding Celestron Nexstar equipment. Here are his comments:
"The unfortunate fact is that the corrector, primary mirror and secondary mirror on each individual scope is a matched set. In fact, on Celestron Schmidt-Cassegrain scopes the secondary is hand figured to further improve the match. So, Celestron does not manufacture individual correctors that find their way into the market.
So, there are three possible fixes for your dilemma:
· Try to find someone via the Internet that has an 8" Celestron optical tube that is damaged in some other way and purchase the corrector/secondary and install on your scope. This is the least desirable since the primary mirror on your scope won't match and the optical performance will suffer. Perhaps the primary mirror could also be changed out from the used scope you purchase.
· Try to find a used Celestron or Meade 8" optical tube and replace the entire optical tube on your scope. This is a good route to go providing the used optical tube is in good condition. The more recent the manufacture of the tube the better as Celestron and Meade's optics have been very good in recent years, but back in the 80s and early 90s they were not so consistent.
· Return it Celestron for repair. They will replace the corrector, primary mirror and secondary mirror with all new components. In fact, you should be able to XLT coatings. This is probably the best option since you will have a like-new scope that will almost certainly perform better than any used optical tube that you might find. And it is likely to be about the same cost as most used optical tubes."
I just went ahead and ordered a new OTA. It arrived yesterday...